Preparation method and application of PVDF-TrFE chitosan hydrogel
阅读说明：本技术 一种PVDF-TrFE壳聚糖水凝胶的制备方法及其应用 (Preparation method and application of PVDF-TrFE chitosan hydrogel ) 是由 李洁 胡智锐 魏晓童 王晨 韩晶 李迎春 王文生 于 2021-09-28 设计创作，主要内容包括：本发明涉及压电压阻复合柔性传感器制备领域,具体是一种PVDF-TrFE壳聚糖水凝胶的制备方法及其应用,以PEDOT:PSS为导电填料,以PVDF-TrFE为压电材料,并采用生物相容性好的交联壳聚糖季铵盐溶液作为柔性网络骨架,经热凝胶成型得到PVDF-TrFE/交联壳聚糖季铵盐水凝胶。本发明制备工艺简便,成本低廉,制得水凝胶还具有一定的机械强度以及应变传感性能,同时具有压电效应和压阻效应,能够同时检测静态力以及动态力,可以做到相互转化,为可拉伸、高灵敏的应变传感导电水凝胶的构建提供了新思路。(The invention relates to the field of piezoelectric piezoresistive composite flexible sensor preparation, in particular to a preparation method and application of PVDF-TrFE chitosan hydrogel. The preparation method is simple and convenient in preparation process and low in cost, the prepared hydrogel also has certain mechanical strength and strain sensing performance, and simultaneously has the piezoelectric effect and the piezoresistive effect, static force and dynamic force can be detected simultaneously, mutual transformation can be realized, and a new idea is provided for the construction of the stretchable and high-sensitivity strain sensing conductive hydrogel.)
1. A preparation method of PVDF-TrFE chitosan hydrogel is characterized by comprising the following steps:
s1) preparing PVDF-TrFE/cross-linked chitosan quaternary ammonium salt concentrated solution
S101), preparing PEDOT (PSS)/chitosan quaternary ammonium salt water solution: adding PEDOT, PSS conductive liquid and deionized water into a beaker, then adding chitosan quaternary ammonium salt, stirring for 5min, and standing for 24h to obtain PEDOT, PSS/chitosan quaternary ammonium salt water solution;
s102) preparing PEDOT, namely PSS/cross-linked chitosan quaternary ammonium salt solution: adding epoxy chloropropane into the PEDOT/PSS/chitosan quaternary ammonium salt solution obtained in the step S101), stirring at a constant temperature for 4h, continuously dropwise adding a sodium hydroxide solution during the reaction to maintain the pH value of the reaction system at 10, naturally cooling to room temperature after the reaction is finished, and regulating the pH value to 7 by using a hydrochloric acid solution to obtain the PEDOT/PSS/cross-linked chitosan quaternary ammonium salt solution;
s103), dialysis: pouring the PEDOT, PSS/cross-linked chitosan quaternary ammonium salt solution in the step S102) into a dialysis bag, then placing the dialysis bag into a beaker, measuring deionized water, adding into the beaker, dialyzing for 72h, and changing the deionized water every 24 h;
s104) preparing a PVDF-TrFE solution: adding PVDF-TrFE into the DMSO solution, stirring at room temperature for 30min, and performing ultrasonic treatment for 60min to ensure complete dissolution of PVDF-TrFE;
pouring the dialyzed PEDOT, namely PSS/cross-linked chitosan quaternary ammonium salt solution in the step S103) into a beaker, then adding glycerol, then adding the DMSO solution dissolved with the PVDF-TrFE, then concentrating in a water bath magnetic stirrer at the concentration temperature of 70 ℃ for 7h to obtain PVDF-TrFE cross-linked chitosan quaternary ammonium salt concentrated solution, and pouring the PVDF-TrFE cross-linked chitosan quaternary ammonium salt concentrated solution into a glass vessel for standing to remove bubbles for later use;
s2) preparing PVDF-TrFE/chitosan quaternary ammonium salt hydrogel
S201), ultrasonic treatment: placing the beaker containing the PVDF-TrFE crosslinked chitosan concentrated solution in the step S104) in a magnetic water bath, stirring for 1h, and performing ultrasonic treatment for 1h to obtain a blue-black PVDF-TrFE/chitosan quaternary ammonium salt hydrogel precursor solution;
s202), pouring the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel precursor solution obtained in the step S201) into a mould, and then carrying out thermal gel forming at the baking temperature of 70 ℃ for 4h to obtain the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
s3, detection, assay, analysis, characterization
Detecting, analyzing and characterizing the mechanical property and the strain sensing property of the prepared PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
analyzing the mechanical property by a digital universal stretcher;
analyzing the GF factors by using a digital universal stretcher;
performing strain sensing performance analysis by using a Keithley MM 6500-word universal meter;
and (4) conclusion: the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel can realize the synergy of piezoelectric-piezoresistive effect by adding the PEDOT, the PSS conductive liquid and the PVDF-TrFE solution, and the obtained PVDF-TrFE/chitosan quaternary ammonium salt hydrogel has excellent strain sensing performance and can be used for preparing a stretchable high-sensitivity hydrogel strain sensor.
2. The method for preparing PVDF-TrFE chitosan hydrogel as claimed in claim 1, wherein in step S104), the concentration is performed to 20% of the original volume by using a water bath magnetic stirrer.
3. The preparation method of the piezoelectric-piezoresistive composite flexible sensor according to claim 1, wherein the feeding mass ratio of the chitosan quaternary ammonium salt to the PEDOT to PSS conductive liquid is 2: 5, the feeding mass ratio of the sugar quaternary ammonium salt to the PVDF-TrFE solution is 2: 0.1 to 0.5.
4. The process as claimed in claim 1, wherein the feed ratio of the chitosan quaternary ammonium salt to the PVDF-TrFE solution is 0.05-0.25: 1.
5. the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel prepared by the preparation method according to claim 1 is used as a strain sensor, and is characterized in that two wires are placed in a mold, the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel is poured into the mold, a flexible sensor is prepared in a hot baking forming mode, a sensor sample strip is taken off from the mold after 8 hours and 70 ℃ hot baking, and the piezoelectric-piezoresistive composite flexible sensor is obtained by cutting.
6. A method for making a piezo-piezoresistive composite flexible sensor according to claim 5, wherein the cut dimensions are 60mm long, 1mm wide and 2mm high.
7. The method as claimed in claim 5, wherein the conductive wire is a copper wire with a lead length of 30 mm.
Technical Field
The invention relates to the field of piezoelectric piezoresistive composite flexible sensors, in particular to a preparation method and application of PVDF-TrFE chitosan hydrogel.
Background
The existing flexible strain sensors are mainly divided into a piezoelectric type and a piezoresistive type. The piezoelectric sensor has a fast response time, and is suitable for detecting dynamic signals, such as transient force changes, deformation speed, and the like, but the piezoelectric sensing signals cannot reflect the final stress state and strain state of an object. The advantages of the piezoresistive sensor are often reflected in the detection of static force, and the stress state and the deformation state of an object are detected in real time according to the magnitude of a current value. However, the piezoresistive sensor also has the disadvantages of being unable to sense the stress direction and the bending strain direction of the object, being insensitive to the strain rate of the object, and the like. Therefore, in order to obtain a strain sensor with high sensitivity, it is necessary to develop a piezoelectric piezoresistive composite sensing material with unique structure and high sensitivity.
The piezoresistive sensors are mainly distinguished by various conductive fillers, so that research on the piezoresistive sensors is complete at present, high response can be achieved, and the piezoresistive sensors are difficult to continue to work under the conditions of dynamic force detection and lack of an external power supply. And the design of piezoelectric sensors can address this challenge.
Since the japanese scholars report the strong piezoelectric activity of the ferroelectric polymer polyvinylidene fluoride (PVDF) for the first time, the PVDF becomes the preferred material for the flexible piezoelectric sensor. Research shows that after trifluoroethylene (TrFE) is added into polyvinylidene fluoride (PVDF), the formation of a beta piezoelectric phase can be promoted due to the steric hindrance effect. More particularly, PVDF-TrFE forms primarily the beta phase under different molding processes. Based on this feature, PVDF-TrFE has received attention from many researchers as a typical piezoelectric material.
The most widespread method of preparation of electrically conductive hydrogels is currently direct doping or incorporation of electron-conducting components into the hydrogel matrix. However, simple mixing methods often result in heterogeneous separation or aggregation of the conductive filler, resulting in reduced performance. Therefore, proper design of the conductive hydrogel structure is particularly important.
The preparation difficulty of the core layer of the piezoelectric-piezoresistive dual-mode composite sensor is how to disperse a PVDF-TrFE piezoelectric phase in a hydrogel system, and due to the unique property of the PVDF-TrFE, the PVDF-TrFE can be directly added into the hydrogel system and the situation that the PVDF-TrFE cannot be dissolved frequently occurs, so that DMSO is selected to completely dissolve the PVDF-TrFE, the distribution of the PVDF-TrFE dispersed phase is optimized through the dipole effect between the PVDF-TrFE and a chitosan quaternary ammonium salt chain, the synergistic effect of the piezoelectric effect and the piezoresistive effect is achieved, and the strain sensing performance of the hydrogel sensor is further improved.
Disclosure of Invention
The invention discloses a preparation method of PVDF-TrFE chitosan hydrogel and application thereof, aiming at solving the problems, the preparation process is simple and convenient, the cost is low, the prepared hydrogel also has certain mechanical strength and strain sensing performance, and simultaneously has piezoelectric effect and piezoresistive effect, can simultaneously detect static force and dynamic force, can realize mutual transformation, and provides a new thought for the construction of stretchable and highly sensitive strain sensing conductive hydrogel.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of PVDF-TrFE chitosan hydrogel comprises the following steps:
s1) preparing PVDF-TrFE/cross-linked chitosan quaternary ammonium salt concentrated solution
S101), preparing PEDOT (PSS)/chitosan quaternary ammonium salt water solution: adding PEDOT, PSS conductive liquid and deionized water into a beaker, then adding chitosan quaternary ammonium salt, stirring for 5min, and standing for 24h to obtain PEDOT, PSS/chitosan quaternary ammonium salt water solution;
s102) preparing PEDOT, namely PSS/cross-linked chitosan quaternary ammonium salt solution: adding epoxy chloropropane into the PEDOT/PSS/chitosan quaternary ammonium salt solution obtained in the step S101), stirring at a constant temperature for 4h, continuously dropwise adding a sodium hydroxide solution during the reaction to maintain the pH value of the reaction system at 10, naturally cooling to room temperature after the reaction is finished, and regulating the pH value to 7 by using a hydrochloric acid solution to obtain the PEDOT/PSS/cross-linked chitosan quaternary ammonium salt solution;
s103), dialysis: pouring the PEDOT, PSS/cross-linked chitosan quaternary ammonium salt solution in the step S102) into a dialysis bag, then placing the dialysis bag into a beaker, measuring deionized water, adding into the beaker, dialyzing for 72h, and changing the deionized water every 24 h;
s104) preparing a PVDF-TrFE solution: adding PVDF-TrFE into the DMSO solution, stirring at room temperature for 30min, and performing ultrasonic treatment for 60min to ensure complete dissolution of PVDF-TrFE;
pouring the dialyzed PEDOT, namely PSS/cross-linked chitosan quaternary ammonium salt solution in the step S103) into a beaker, then adding glycerol, then adding the DMSO solution dissolved with the PVDF-TrFE, then concentrating in a water bath magnetic stirrer at the concentration temperature of 70 ℃ for 7h to obtain PVDF-TrFE cross-linked chitosan quaternary ammonium salt concentrated solution, and pouring the PVDF-TrFE cross-linked chitosan quaternary ammonium salt concentrated solution into a glass vessel for standing to remove bubbles for later use;
s2) preparing PVDF-TrFE/chitosan quaternary ammonium salt hydrogel
S201), ultrasonic treatment: placing the beaker containing the PVDF-TrFE crosslinked chitosan concentrated solution in the step S104) in a magnetic water bath, stirring for 1h, and performing ultrasonic treatment for 1h to obtain a blue-black PVDF-TrFE/chitosan quaternary ammonium salt hydrogel precursor solution;
s202), pouring the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel precursor solution obtained in the step S201) into a mould, and then carrying out thermal gel forming at the baking temperature of 70 ℃ for 4h to obtain the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
s3, detection, assay, analysis, characterization
Detecting, analyzing and characterizing the mechanical property and the strain sensing property of the prepared PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
analyzing the mechanical property by a digital universal stretcher;
analyzing the GF factors by using a digital universal stretcher;
performing strain sensing performance analysis by using a Keithley MM 6500-word universal meter;
and (4) conclusion: the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel can realize the synergy of piezoelectric-piezoresistive effect by adding the PEDOT, the PSS conductive liquid and the PVDF-TrFE solution, and the obtained PVDF-TrFE/chitosan quaternary ammonium salt hydrogel has excellent strain sensing performance and can be used for preparing a stretchable high-sensitivity hydrogel strain sensor.
Preferably, in step S104), the concentration is performed to 20% of the original volume by using a water bath magnetic stirrer.
Preferably, the feeding mass ratio of the chitosan quaternary ammonium salt to the PEDOT/PSS conductive liquid is 2: 5, the feeding mass ratio of the sugar quaternary ammonium salt to the PVDF-TrFE solution is 2: 0.1 to 0.5.
Preferably, the feeding ratio of the chitosan quaternary ammonium salt to the PVDF-TrFE solution is 0.05-0.25: 1.
the invention also provides application of the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel prepared by the preparation method of the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel as a strain sensor, wherein the application comprises the steps of placing two leads in a mold, pouring the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel into the mold, preparing the flexible sensor in a hot drying molding mode, taking down a sensor sample strip from the mold after 8 hours and 70 ℃ hot drying, and cutting to obtain the piezoelectric-piezoresistive composite flexible sensor.
Preferably, the cutting size is 60mm in length, 1mm in width and 2mm in height.
Preferably, the lead is a copper lead with the lead-out length of 30 mm.
Compared with the prior art, the invention has the beneficial effects that:
the invention uses DMSO as a solvent to ultrasonically dissolve PVDF-TrFE-TrFE, and the reaction between the PVDF-TrFE-TrFE and PEDOT: the PSS aqueous solution is physically mixed to form a conductive network. The preparation method is simple and convenient in preparation process and low in cost, the prepared hydrogel also has certain mechanical strength and strain sensing performance, and simultaneously has the piezoelectric effect and the piezoresistive effect, static force and dynamic force can be detected simultaneously, mutual transformation can be realized, and a new idea is provided for the construction of the stretchable and high-sensitivity strain sensing conductive hydrogel.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of a process for preparing PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
FIG. 2 shows the conductivity of PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
FIG. 3 is a stress-strain curve of PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
FIG. 4 is a GF factor analysis of PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
FIG. 5 is the piezoresistive properties of PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
FIG. 6 is the piezoelectric properties of PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
FIG. 7 is a voltage signal and piezoresistive signal response diagram of PVDF-TrFE/chitosan quaternary ammonium salt hydrogel.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
In order to make the technical solutions of the present application better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Example 1
Technical scheme
The chemical materials used were: the composite material comprises chitosan quaternary ammonium salt, epichlorohydrin, sodium hydroxide, hydrochloric acid, glycerol, PVDF-TrFE fibrous material, PEDOT, PSS and deionized water, wherein the combined preparation amount is as follows: in grams, milliliters and centimeters3As a unit of measure
Chitosan quaternary ammonium salt: HACC solid 99.5% 2.0 g. + -. 0.001g
Epoxy chloropropane: c3H5ClO liquid 99.5% 4mL + -0.001 mL
Sodium hydroxide: NaOH solid 99.5% 5 g. + -. 0.001g
Hydrochloric acid: HCl liquid 99.5% 23 mL. + -. 0.001mL
Glycerol: c3H8O399.5% of liquid 1mL +/-0.001 mL
PVDF-TrFE fibrous 99.5% 100-500mg
PEDOT PSS liquid solid 99.5% 5ml
Deionized water: h299.99% of O liquid 5000mL +/-50 mL
As shown in fig. 1, a preparation method of PVDF-TrFE chitosan hydrogel includes the following steps:
s1) preparing PVDF-TrFE/cross-linked chitosan quaternary ammonium salt concentrated solution
S101), preparing PEDOT (PSS)/chitosan quaternary ammonium salt water solution: adding 5mL of PEDOT, PSS conductive liquid and 200mL of +/-0.001 mL of deionized water into a beaker, then adding 2.0g of +/-0.001 g of chitosan quaternary ammonium salt, stirring for 5min, and standing for 24h to obtain PEDOT, PSS/chitosan quaternary ammonium salt aqueous solution;
s102) preparing PEDOT, namely PSS/cross-linked chitosan quaternary ammonium salt solution: adding 4.72g of epoxy chloropropane into the PEDOT/PSS/chitosan quaternary ammonium salt aqueous solution obtained in the step S101), stirring at a constant temperature for 4h, continuously dropwise adding a sodium hydroxide solution during the reaction to maintain the pH of the reaction system at 10, naturally cooling to room temperature after the reaction is finished, and adjusting the pH value to 7 by using 2mL +/-0.001 mL of hydrochloric acid solution to obtain the PEDOT/PSS/crosslinked chitosan quaternary ammonium salt aqueous solution;
s103), dialysis: pouring the PEDOT, PSS/cross-linked chitosan quaternary ammonium salt solution in the step S102) into a dialysis bag, then placing the dialysis bag into a beaker, measuring 500mL +/-0.001 mL of ionized water, adding into the beaker, dialyzing for 72h, and changing the deionized water every 24 h;
s104) preparing a PVDF-TrFE solution: adding 100-500mg PVDF-TrFE into 25ml DMSO solution, stirring at room temperature for 30min, and performing ultrasonic treatment for 60min to ensure complete dissolution of PVDF-TrFE;
pouring 200mL +/-0.001 mL of PEDOT (sodium sulfovinate)/PSS/cross-linked chitosan quaternary ammonium salt solution dialyzed in the step S103) into a beaker, then adding 1mL of glycerol, then adding the DMSO solution dissolved with the PVDF-TrFE, then concentrating in a water bath magnetic stirrer to 40mL, wherein the concentration temperature is 70 ℃, and the concentration time is 7 hours, so as to obtain a PVDF-TrFE cross-linked chitosan quaternary ammonium salt concentrated solution, and pouring the PVDF-TrFE cross-linked chitosan quaternary ammonium salt concentrated solution into a glass vessel to stand and remove bubbles for later use;
s2) preparing PVDF-TrFE/chitosan quaternary ammonium salt hydrogel
S201), ultrasonic treatment: placing the beaker containing the PVDF-TrFE crosslinked chitosan concentrated solution in the step S104) in a magnetic water bath, stirring for 1h, and performing ultrasonic treatment for 1h to obtain a blue-black PVDF-TrFE/chitosan quaternary ammonium salt hydrogel precursor solution;
s202), pouring the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel precursor solution obtained in the step S201) into a mould, and then carrying out thermal gel forming at the baking temperature of 70 ℃ for 4h to obtain the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
s3, detection, assay, analysis, characterization
Detecting, analyzing and characterizing the mechanical property and the strain sensing property of the prepared PVDF-TrFE/chitosan quaternary ammonium salt hydrogel;
analyzing the mechanical property by a digital universal stretcher;
analyzing the GF factors by using a digital universal stretcher;
performing strain sensing performance analysis by using a Keithley MM 6500-word universal meter;
and (4) conclusion: the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel can realize the synergy of piezoelectric-piezoresistive effect by adding the PEDOT, the PSS conductive liquid and the PVDF-TrFE solution, and the obtained PVDF-TrFE/chitosan quaternary ammonium salt hydrogel has excellent strain sensing performance and can be used for preparing a stretchable high-sensitivity hydrogel strain sensor.
In step S104), the mixture is concentrated to 20% of the original volume by a water bath magnetic stirrer.
The feeding mass ratio of the chitosan quaternary ammonium salt to the PEDOT/PSS conductive liquid is 2: 5, the feeding mass ratio of the sugar quaternary ammonium salt to the PVDF-TrFE solution is 2: 0.1 to 0.5.
The feeding ratio of the chitosan quaternary ammonium salt to the PVDF-TrFE solution is 0.05-0.25: 1.
the invention also provides application of the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel prepared by the preparation method of the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel as a strain sensor, wherein the application comprises the steps of placing two leads in a mold, pouring the PVDF-TrFE/chitosan quaternary ammonium salt hydrogel into the mold, preparing the flexible sensor in a hot drying molding mode, taking down a sensor sample strip from the mold after 8 hours and 70 ℃ hot drying, and cutting to obtain the piezoelectric-piezoresistive composite flexible sensor.
The cutting size is 60mm in length, 1mm in width and 2mm in height.
The lead is a copper lead with the lead-out length of 30 mm.
As shown in fig. 2, the hydrogel incorporated into the circuit to illuminate the small bulb, demonstrating its electrical conductivity.
As shown in FIG. 3, the stress-strain curves of the hydrogels with different amounts of PVDF-TrFE are shown, and the elongation at break and tensile strength of the hydrogels are comparable to those of the hydrogels with different addition amounts, and the comparison shows that the tensile strength and elongation at break are optimal values when the addition amount is 250mg, so that the addition amount is suitable for the strain sensor.
As shown in FIG. 4, the GF factors of the PVDF-TrFE/PEDOT/PSS chitosan hydrogel show a tendency of increasing first and then decreasing with the addition of PVDF-TrFE, and when the addition amount of PVDF-TrFE is 250mg, the GF factors of the hydrogel prepared by the invention reach the highest value, which can reach 19.24.
As shown in fig. 5, it can be seen that the rate of change of resistance changes regularly with time as the finger is bent, and the rate of change of resistance of the hydrogel also changes when the finger bending angle is different, demonstrating that the PVDF-TrFE/chitosan hydrogel has excellent piezoresistive strain sensing performance.
As shown in FIG. 6, the curve is a curve which is regularly changed along with the change rate of the finger bending voltage along with time, and the voltage change rate of the hydrogel is different when the finger bending angle is different, so that the PVDF-TrFE/chitosan hydrogel has the intentional piezoelectric strain sensing performance.
As shown in FIG. 7, the hydrogel can generate a 40mV voltage signal when compressed, stretched or bent, the signal response rate is fast, and the hydrogel can generate a regular resistance change under the same response, which proves the piezoresistive performance of the hydrogel.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement, component separation or combination and the like made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.